The present invention relates to a fluorine rubber composition used in an image picture forming apparatus, a fixing member, a fixing device, a fixing method, and a method of manufacturing the fixing device.
In an image picture forming apparatus, a toner transferred onto a recording material such as paper or the like is fixed by a fixing device installed in the apparatus.
FIG. 6 is a sectional view of a conventional fixing device. The fixing device which serves to fix a toner 13 transferred onto a recording material 12 comprises a fixing roller 201 being a fixing member, a press roller 102 opposing to the fixing roller 201, and a web 104 impregnated with silicone oil as a lubricant to prevent sticking of toner T to surface layer 203 of the fixing roller 201. The fixing roller 201 and the press roller 102 are formed by coating a core bar 105 with an elastic body 106. A heater 107 as a heat source is disposed in the core bar 105 of the fixing roller 201.
Recording material 12 such as paper or the like with a picture image formed thereon by transferring the toner 13 is caught between the fixing roller 201 and the press roller 102, and is heated and pressed, then the toner 13 is fixed on the recording material 12.
However, the toner 13 increases in viscosity due to the heat. Accordingly, as shown in the partly enlarged view of FIG. 3 showing a state of picture image fixation in a conventional fixing device, a part of the toner 13 on the recording material 12 adheres to the surface of the fixing roller 201. As a result, when the next recording material 12 advances toward the fixing roller 201 heated, the toner 13, increasing in viscosity and adhering to the fixing roller 201, is partially transferred onto the next recording material 12. This process is generally called offset, and frequent generation of offset means the termination of the life of the fixing device.
In order to prevent generation of such offset, in the prior art, the toner is fixed by heat and pressure of the fixing roller 201 and the press roller 102 while applying a lubricant such as silicone oil to the fixing roller 201. There are some different methods of lubricant application to the fixing roller 201. For examples, as shown in FIG. 6, a lubricant is applied to the fixing roller 201 by contacting the web 104 with the fixing roller 201. The web 104 is pressed against the fixing roller 201 by a web pressing roller 108 and is taken up onto a web take-up roller 110 from a web feed roller 109 at a predetermined speed.
However, in a conventional fixing device, the surface layer 203 of the fixing roller 201 is formed of silicone rubber, fluorine rubber or the like. Since the fixing roller 201 is heated, the surface layer 203 of the fixing roller 201 is deteriorated due to the heat. Further, in use of the fixing roller 201 for a long period of time, the surface layer 203 becomes worn and scratched due to sticking of paper and dust. In case the surface layer 203 is worn or scratched, the toner 13 will stick to the surface layer 203 of the fixing roller 201 despite that the surface layer 203 is coated with a lubricant. That is, there are not a few chances of generation of offset even when the surface layer 203 is coated with a lubricant.
A fixing device capable of preventing such offset is disclosed in Japanese Laid-Open Patent No. 4-319980. The fixing device disclosed in Japanese Laid-Open Patent No. 4-319980 comprises a fixing roller and a roller polishing means to polish the fixing roller surface. The fixing roller used is a single-layer roller formed of methyl or methylvinyl type silicone rubber, and the silicone oil used is methylphenyl type silicone oil.
In such fixing roller, the fixing roller surface is always refreshed since the fixing roller surface is polished by the roller polishing means. As a result, generation of offset can be prevented. Also, since a single-layer roller formed of silicone rubber is employed, polishing the fixing roller surface does not cause the under layer material to be exposed, thereby improving the durability.
However, in such prior art fixing device, the optimum conditions for roller polishing vary with various factors such as grain sizes of polishing material, grain shapes, its contents in silicone oil, abutment pressures to the fixing roller of cleaning web as a roller polishing means, abutment areas, fiber density of web, and material quality of roller rubbers. Accordingly, it is difficult to find and maintain optimum values in relation to a number of these factors. Further, as the fixing roller surface is polished, the roller will be reduced in diameter through use for a long period of time. Consequently, the above-mentioned factors at their optimum values are influenced, gradually going wrong.
The present invention is intended to improve the durability of the fixing member, preventing generation of offset reliably for a long period of time by lessening the amount of toner sticking to the fixing member surface without polishing the fixing member surface of a roller or the like.
A fluorine rubber composition of the present invention, used for the surface layer material of a fixing member to fix a toner transferred onto a recording material, comprises:
(a) fluorine rubber having a polymerization degree based on vinylidene fluoride; and
(b) at least one selected from the group consisting of a reinforcing agent, an antacid, a vulcanizing agent, a vulcanization accelerator, a spherical filler, and an organic solvent.
A fixing member of the present invention for fixing a toner transferred onto a recording material comprises:
a base material and
a surface layer material disposed on the base material,
wherein the surface layer material contains fluorine rubber having a polymerization degree based on vinylidene fluoride.
A fixing device of the present invention for fixing a toner transferred onto the surface of a recording material comprises:
a fixing roller;
a press roller disposed opposing the fixing roller; and
a web to apply a lubricant to the surface of the fixing roller,
wherein the fixing roller comprises a base material and a surface layer material disposed on the surface of the base material;
the surface layer material contains fluorine rubber having a polymerization degree based on vinylidene fluoride; and
a recording material having the toner transferred thereon passes between the fixing roller and the press roller while being pressed by the fixing roller and the press roller so that the surface layer material comes in contact with the toner, and thereby, the toner is fixed on the recording material.
A fixing method of the present invention comprises:
(a) a step of transferring a toner onto the surface of a recording material:
(b) a step of passing the recording material, having the toner transferred thereon, between a fixing roller and a press roller, under pressures applied by the fixing roller and the press roller,
wherein the fixing roller comprises a base material and a surface layer material disposed on the surface of the base material;
the recording material passes between the rollers in a manner such that the toner is positioned at the fixing roller side;
the surface layer material contains fluorine rubber having a polymerization degree based on vinylidene fluoride; and
(c) a step of fixing the toner, pressed by the fixing roller and the press roller, on the surface of the recording material.
A method of manufacturing a fixing device of the present invention for fixing a toner transferred onto the surface of a recording material comprises the steps of:
(a) manufacturing a fixing roller; and
(b) manufacturing a press roller,
wherein the step of manufacturing the fixing roller comprises the steps of:
(1) manufacturing a paint;
wherein the step of manufacturing the paint includes a step of mixing and dispersing fluorine rubber having a polymerization degree based on vinylidene fluoride, a vulcanizing agent, and a solvent;
(2) applying the paint onto the surface of a base material having a spherical shape; and
(3) drying and hardening the paint applied to the surface of the base material to form a surface layer material.
Preferably, the fluorine rubber contains at least one copolymer selected from the group consisting of a copolymer of tetrafluoroethylene, vinylidene fluoride and hexafluoropropylene; a copolymer of tetrafluoroethylene, vinylidene fluoride and propylene; and a copolymer of vinylidene fluoride and hexafluoropropylene.
By the above configuration, the amount of toner sticking to the surface of a fixing member is reduced. Accordingly, generation of offset can be reliably prevented for a long period of time. Further, the durability of the fixing member will be improved.